Vehicles can be powered by operation of engines. These engines may consume fuel and having moving parts (e.g., pistons in cylinders) lubricated by oil. During operation of the engines in certain operational conditions (e.g., low fueling levels or during idle operation where an engine is operating but is not producing power to propel a vehicle), oil in cylinders of the engine may work upward and pool on top of pistons in the cylinders. At least some of this pooled oil may be expelled from the cylinders and/or engine via the flow of exhaust exiting the cylinders. The upward movement, pooling, and/or expulsion of the oil may be referred to as oil carryover.
Vehicles having systems that treat or re-use the exhaust from the cylinders may be damaged by oil carryover. For example, an exhaust aftertreatment system may chemically react one or more chemicals with the exhaust in order to reduce the amount of certain constituents in the exhaust. Exhaust gas recirculation (EGR) systems may recycle at least some of the exhaust and re-introduce the exhaust back into at least some of the cylinders in the engine.
But, the aftertreatment systems and EGR systems may be damaged by the presence of oil in the exhaust. Sulfur or other constituents in the exhaust due to oil carryover can damage or destroy chemical catalysts in the aftertreatment systems. Oil in the exhaust can damage or destroy cooling components of the EGR systems that are needed to cool the recirculated portion of the exhaust prior to re-introducing the exhaust back into the cylinders.
One existing attempt to prevent or reduce damage to aftertreatment systems and/or EGR systems from oil carryover includes temporarily increasing the load on the engine. This heats the exhaust and can burn the oil out of the exhaust. But, this solution also significantly increases the amount of fuel consumed by the engine and is not a fuel-efficient manner of reducing or eliminating oil carryover. This can help in removing, or blowing out, the oil pooled on top of the cylinders into the exhaust leaving the cylinders. But, this solution also increases the amount of oil in the exhaust for a temporary time period, which still can damage or destroy the catalysts in the aftertreatment systems and/or the cooling components of the EGR systems. Additionally, this solution can cause a significant amount of oil to be introduced into one or more cylinders of the engine. This oil cannot be easily compressed by the piston in a compression chamber of a cylinder. As a result, the engine may be damaged when a connecting rod of a cylinder attempts to compress the air (and oil) in the cylinder.